Forensic integrity of blood alcohol sampling in the emergency department, Part II: Establishing quality goals of turnaround time with Monte Carlo simulation.

Abstract

Introduction: In the emergency department (ED), the turnaround time (TAT) for forensic blood alcohol sampling is a critical determinant of legal admissibility. Due to the pharmacokinetics of ethanol, delays in sampling lead to metabolic decay, potentially resulting in pharmacokinetic false negatives (FN_pk). This study aims to establish objective, evidence-based quality goals for intra-ED TAT using Monte Carlo simulation to preserve forensic reliability.

Materials and methods: Data were collected from 121 forensic cases at a major metropolitan university hospital in 2025. A Monte Carlo simulation (N = 50,000 iterations) was performed to model the probability of FN_pk based on ethanol elimination rate (β), analytical imprecision (CV), and extra-ED versus intra-ED TAT components. Probability density functions (PDFs) were fitted using Weibull and Gamma distributions to characterize observed clinical and logistical data.

Results: The simulation revealed a baseline P(FN_pk) of 7.0% for the intra-ED phase, increasing to 7.6% when including extra-ED transport. Quality goals were derived for three tiers: optimal (TAT_95%) at 134 minutes, acceptable (TAT_80%) at 214 minutes, and minimum (TAT_60%) at 273 minutes. Regression analysis showed that for every 1% increase in assay CV, the TAT quality goal erodes by 2.7 to 3.3 minutes. The logistic process was found efficient, with an Index of Logistic Reliability (I_LR) of 86.4%.

Conclusions: Monte Carlo simulation effectively translates pharmacokinetic variables into actionable forensic quality goals. Current ED performance requires process improvement, particularly in the request-transmission phase, to minimize FN_pk and ensure forensic equity.